I had two sheds with similar treated runners. I’m in Minnesota so needed to make sure it didn’t heave. I dug 8 holes approx 30” deep, put out a leveling grid, and filled the filled the holes most of the way with class 5 gravel. I put some concrete blocks on the class 5 and leveled them against each other. The shed maker should have specs on how many supports are needed. I added a couple more. The shed is then placed on these blocks. 6 years and still solid as as rock.